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Refactoring the mmap interface. The controlling pragma is now "mmap_size"

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instead of "mmap_limit".  Also change SQLITE_CONFIG_MMAP_LIMIT and
SQLITE_FCNTL_MMAP_LIMIT to SQLITE_CONFIG_MMAP_SIZE and
SQLITE_FCNTL_MMAP_SIZE, respecctively.  
The default mmap_size is now always 0, meaning that
memory mapped I/O is off by default.  There is a new compile-time option
SQLITE_MAX_MMAP_SIZE that determines a hard upper bound on the mmap_size.
Setting SQLITE_MAX_MMAP_SIZE to zero disables the memory-mapped I/O logic
and causes it to be omitted from the build.  An extra argument is added
to SQLITE_CONFIG_MMAP_SIZE that can optionally lower the SQLITE_MAX_MMAP_SIZE
at start-time. The SQLITE_MAX_MMAP_SIZE is zero for platforms where we 
know that it does not work, meaning that it cannot be turned on by mistake
on those platforms.

FossilOrigin-Name: ea1404a10abd7f68e1f8e0708c8a3199d1f79665
This commit is contained in:
drh
2013-04-15 17:03:42 +00:00
parent a1710cc2ea
commit 9b4c59fa1b
31 changed files with 245 additions and 213 deletions
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26
src/pager.c
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@@ -658,7 +658,7 @@ struct Pager {
u8 bUseFetch; /* True to use xFetch() */
int nMmapOut; /* Number of mmap pages currently outstanding */
sqlite3_int64 mxMmap; /* Desired maximum mmap size */
sqlite3_int64 szMmap; /* Desired maximum mmap size */
PgHdr *pMmapFreelist; /* List of free mmap page headers (pDirty) */
/*
** End of the routinely-changing class members
@@ -774,10 +774,10 @@ static const unsigned char aJournalMagic[] = {
** The macro USEFETCH is true if we are allowed to use the xFetch and xUnfetch
** interfaces to access the database using memory-mapped I/O.
*/
#ifdef SQLITE_DISABLE_MMAP
# define USEFETCH(x) 0
#else
#if SQLITE_MAX_MMAP_SIZE>0
# define USEFETCH(x) ((x)->bUseFetch)
#else
# define USEFETCH(x) 0
#endif
/*
@@ -3370,16 +3370,16 @@ void sqlite3PagerSetCachesize(Pager *pPager, int mxPage){
}
/*
** Invoke SQLITE_FCNTL_MMAP_LIMIT based on the current value of mxMmap.
** Invoke SQLITE_FCNTL_MMAP_SIZE based on the current value of szMmap.
*/
static void pagerFixMaplimit(Pager *pPager){
#if !defined(SQLITE_DISABLE_MMAP)
#if SQLITE_MAX_MMAP_SIZE>0
sqlite3_file *fd = pPager->fd;
if( isOpen(fd) ){
sqlite3_int64 mx;
pPager->bUseFetch = (fd->pMethods->iVersion>=3) && pPager->mxMmap>0;
mx = pPager->mxMmap;
sqlite3OsFileControlHint(pPager->fd, SQLITE_FCNTL_MMAP_LIMIT, &mx);
sqlite3_int64 sz;
pPager->bUseFetch = (fd->pMethods->iVersion>=3) && pPager->szMmap>0;
sz = pPager->szMmap;
sqlite3OsFileControlHint(pPager->fd, SQLITE_FCNTL_MMAP_SIZE, &sz);
}
#endif
}
@@ -3387,8 +3387,8 @@ static void pagerFixMaplimit(Pager *pPager){
/*
** Change the maximum size of any memory mapping made of the database file.
*/
void sqlite3PagerSetMmapLimit(Pager *pPager, sqlite3_int64 mxMmap){
pPager->mxMmap = mxMmap;
void sqlite3PagerSetMmapLimit(Pager *pPager, sqlite3_int64 szMmap){
pPager->szMmap = szMmap;
pagerFixMaplimit(pPager);
}
@@ -4766,7 +4766,7 @@ int sqlite3PagerOpen(
/* pPager->pBusyHandlerArg = 0; */
pPager->xReiniter = xReinit;
/* memset(pPager->aHash, 0, sizeof(pPager->aHash)); */
/* pPager->mxMmap = SQLITE_DEFAULT_MMAP_LIMIT // will be set by btree.c */
/* pPager->szMmap = SQLITE_DEFAULT_MMAP_SIZE // will be set by btree.c */
*ppPager = pPager;
return SQLITE_OK;